Arthur Johannson asks about Magnatek Ballasts in APD #244. I do not have my
catalog at hand, so I am answering his question from memory - a risky
endeavor! However, I believe he is describing a very common type of
"magnetic" ballast. Magnatek is a very well-known brand of magnetic
ballasts. They are well made. Ballasts seem to be poorly understood, and the
differences between the various kinds are also poorly understood.

I will stick my neck out, and try to describe how ballasts work, and the
differences between them. Again, this is risky, as it is a lot easier to
describe these devices with drawings. Also, I am NOT an engineer. This will
not be as organized nor as clear as an Engineer would say it, but I will do
my best.

The "ballast" for any fluorescent bulb is mostly a
current limiting device. Once the "arc" is started between
the ends of the tube, an essentially unlimited direct "short circuit"
is developed. The best illustration that immediately comes to mind is
a bolt of lightning. Lighting does not just suddenly blast a
giant spark from cloud to ground. First, in an extremely short
time just before the bolt of lightning, an "ion trail" is
established between the cloud and the earth. In other words, a
"pathway" is established in the air, the pathway made up of "ionized"
molecules of the gases that air is made of. Then, the giant "spark,"
the actual "lightning bolt" follows that pathway in an enormous burst
of energy. The loud "Bang" is generated from the suddenly heated air
as the spark jumps from ground to cloud. (The main "bolt" most often
actually jumps from the ground up to the cloud, not the other
way around.) The arc in a fluorescent tube is similar, in that it must
be controlled to keep a sort of miniature "lightning bolt" from
ruining the fluorescent bulb.

Now I will 'backtrack' a bit. If you could take the white
"phosphor" coating off of the inside of an ordinary fluorescent bulb,
you would see that there is a "filament," a tightly coiled wire, that
runs from one of the pins in the end of the bulb to the other pit at
that end of the bulb. There is a "filament" on both ends of
the bulb. They are usually covered with a whitish powdery stuff. The
powdery stuff is a material that "boils off" lots of electrons when
heated. The filament is the thing that actually "fails" when a
fluorescent bulb wears out. Either the filament burns out, or all of
the powdery stuff has "boiled off"

What is in the clear space from one end of the bulb to the other?
That depends upon several Engineering decisions made by the folks that
designed that particular bulb. However, it is always a
pretty good vacuum, with a small amount of some gas or other.
If you look at a Neon sign that is not lit, it has a pretty good
vacuum, with a teeeny tiny bit of Neon gas. It looks like just "clear
glass" until it is lit. When an arc of electrons passes through that
gas, it glows with the familiar reddish orange "NEON" color.
In the fluorescent bulb, you get an arc that generates ultraviolet
light. The Ultraviolet from the arc bangs right up against that
white powder that coats the inside of the bulb, and the powder
glows. Electricity passes through the very thin, almost a
vacuum, gas in the bulb, generating ultraviolet light, which bangs
into the powder, which generates visible light. Ultraviolet
light has a very short wavelength, and we cannot see it.
(Bees and many other insects, on the other hand, have really
tiny eyes, and they see ultraviolet light just fine! In
fact, flowers (that show pretty colors to our big eyes) reflect the
Ultraviolet light in sunlight very strongly, and appear "bright bee
white" to a honey bee. We see colors, they see "white.") ( :-) )

When a fluorescent bulb is "started," one or both of the filaments
at the ends of the bulb is heated by electricity, and "boils off" a
cloud of electrons, which quickly moves down the tube until this cloud
of electrons fills the bulb. (actually, the electrons "ionise" the gas
in the bulb, just like the ion trail that forms the path for a
lightning bolt) Then the arc jumps from one end of the bulb to the
other, and the bulb is "lit."

Without the ballast, the arc would be a direct "short circuit"
between the ends of the bulb, and a huge blast of electricity
would jump through the bulb, and it would either instantly burn up the
filaments, or the bulb would literally explode. Rather like the
lightning bolt I mentioned earlier. An uncontrolled arc through a
fluorescent bulb is BIG trouble for the bulb! Actual bulb explosions
from a "shorted ballast" are very rare, but they can happen. Most
often, if the "ballast" in a fluorescent fixture fails by shorting
out, you hear a loud "pop," accompanied by a very bright flash from
the bulb, then nothing. No noise, no light. The bulb has burned out.
(Actually, the filaments were destroyed by the suddenly uncontrolled
big arc.)

The ballast regulates, or controls, the flow of current through the
arc, one way or another. The magnetic ballast literally "chokes" off
the current at a set point. It does this by taking advantage of some
basic physics. Remember, the electric power in your home is (depending
upon what country you live in) either 50 or 60 cycle alternating
current. In a "cycle," the flow of electicity goes from no flow at
all, up to a set voltage, then back to zero, then goes THE OTHER WAY,
from zero up to the set voltage, then back to zero. The current in
that arc in the bulb does the same thing. It goes from zero to
maximum, back to zero, then the other way, then back to zero. The
ultraviolet light from the arc also goes from zero to maximum, back to
zero, up to maximum, then back to zero. The glow from the phosphor
powder coating the inside of the bulb does the same thing, except the
powder never completely stops glowing.

An alternator, for example the one in your automobile, often spins
magnets inside a set of coils of wire. Any time a wire moves through a
magnetic field, it generates an "ElectroMotive Force," a force
measured in volts. The amount of the force (voltage) depends upon how
strong the magnetic field is, and how FAST the wire moves through the
field. Or, you could move the magnet, and let the wire stand still.
It does not matter which is moving, the magnet, or the wire.

If you pass a current of electricity through a wire, it generates a
magnetic field. Since one of the most basic Laws of Physics can
crudely be stated as "There ain't no such thing as a free lunch," that
magnetic field is exactly opposite to that magnetic field that we were
moving the wire through just a moment ago. If the ends of the wire
(or the ends of a coil made of many turns of wire) are connected, an
electrical current is generated when you move the coil through a
magnetic field. Or, you could move the magnetic field past the coil.
Is does not matter which is moving. Yes, I suppose you could move
both of them at the same time if you wished. ( :-) ) And, any time an
electric current moves through a wire, it generates a magnetic field.

The most difficult concept for most of us is, both things
happen at the same time. You generate a current in the coil of
wire by moving it through a magnetic field, and then that current in
the coil of wire generates another magnetic field. That magnetic
field is exactly opposite to the magnetic field you are
moving the wire through to generate the current. The magnetic fields
"fight", as does the current. I did not say that particularly well.
Sorry!

In a magnetic ballast, the rapid changes in current direction (the "cycles
per second," or "Hertz") makes equally rapid changes in the magnetic field
generated by the coil of wire in the ballast. The magnetic field reverses 120
times a second. (Each "cycle" or "Hertz" goes from zero up, than back to
zero, then the other way, then back to zero.) The corresponding current in
the arc in the bulb is doing the same thing.

The "fighting" magnetic fields and currents in the magnetic ballast "fight"
much stronger as the amount of current flowing through the ballast increases.
This "fighting" impedes, or chokes, the current flow. An individual ballast
is designed by the Engineers so that it will let just exactly the right
amount of current through to light that particular fluorescent bulb, but not
let too much current through. It gets hot from the effects of the "fight."
That heat is totally wasted electricity. You pay for it, but you don't get
any light from it. Magnetic Ballasts are lots simpler and cheaper to make
than Electronic Ballasts. That is probably why they are used so much.

Now, lets go to the actual generation of the light. The white
coating on the inside of the tube, the phosphor, glows from the
ultraviolet light generated from the arc. The arc goes from zero, up
to a maximum, then back to zero, then the other way, than back to
zero. So does the Ultraviolet light. So does the light from the
glowing phosphor! The phosphor is a bit goofy, though. It does not
quite stop glowing between current pulses. It almost stops, but not
quite. If you are in a dark room, you can wave your hand under a
single fluorescent bulb, and you will see multiple hands, as
the light turns on and off and on and off, following the current
cycles. A "strobe" light turns on and off very abruptly and
completely. The fluorescent bulb is kind of lazy, and does not turn
either on or off all that quickly. Its brightness depends mostly upon
a combination of the phosphors used, and upon the amount of current
flowing through it. Too much current, and the filaments will burn
up. Too little, and you don't get much light.

In a common magnetic ballast, you start the arc by flowing a
current through the filaments, heating them until enough electrons
have boiled off to "start" the bulb. Once the bulb is started, the
filaments stop glowing, and the light comes entirely from the
arc. Starting a "pre-heat" bulb can be accomplished by using the
common "starter," which looks like a very small aluminum can with two
pins on one end, or by using a "starter switch." If your light is
started with the switch, you hold the button down for a few seconds,
then release it. If you watch the bulb at the same time, you will see
the ends of the bulb start to glow, first very dimly, then brighter.
When you release the switch, you change the flow of the current from through
the filaments to through the bulb itself. The "starter" does this for you
automatically. The hand starting switch is lots cheaper to make than the
circuitry and the socket for the "starter." It also takes a lot less room in
the "hood" or reflector over your tank.

In a "rapid start ballast," a differently designed fluorescent bulb
is used. "Rapid Start" bulbs are designed to be started by Rapid
Start Ballasts. In these, a small current always flows
through the filaments. The inside of the bulb - the amount of vacuum,
the gases, etc. - is designed to start the arc very very quickly,
without much heating of the filaments. Most "Pre-Heat" bulbs
will not start with magnetic rapid start ballasts. Some can
be induced to start by rubbing the bulb from end to end, thus
capacitatively inducing the arc. If you do get a Pre-Heat
bulb to work with a rapid start ballast, the end or ends of the bulb
will get really black really soon. This is because the filaments
always have a current going through them, something that does not
happen with the normal "pre-heat" ballast. Interestingly enough,
Rapid Start Fluorescent Bulbs work just fine with either the hand
start switch or the "starter." It just does not work the
other way! Rapid Start ballasts are made in Magnetic,
Electronic, or Hybrid kinds. They don't look any different on the
outside. The differences are inside.

Why The Electronic Ballast Gives More Light For The Same Amount Of
Electricity

Remember how the bulb flickers, up to maximum brightness, then
almost to zero, then up, then down, over and over? Well, the
Electronic Ballast does its wizardry and changes the 50 or 60 cycle
alternating current into (usually) 400 cycle alternating current. This
(to make a very crude analogy) keeps the bulb phosphor glowing at
almost the peak brighness almost all of the time. The current cycles
back and forth, going up and down 800 times a second, and the phosphor
never has a chance to quit glowing like it did on ordinary alternating
current. Another advantage to the Electronic Ballast is the fact that
is wastes very little electricity as useless heat. The new
Electronic Ballasts we are installing here in the Aquarium Center draw
slightly over 60 watts of total energy. Yet, they light two, 40 watt
bulbs, and light them much brighter than the Magnetic Ballasts they
are replacing. The Magnetic Ballasts draw more than a hundred watts
of electicicy to light two, 40 watt bulbs. They waste a lot of
electricity as heat. And, the bulbs are not nearly as bright!!

During the Iowa State Fair, there is a severe voltage drop in our area. Too
many other exhibitors, all drawing electricity from under-sized main wiring.
Anyway, we sometimes have voltages UNDER 100 volts. Many Magnetic Ballasts
just quit then. The lights just dim, then go out. They cannot be re-started
until late at night, when all of the other current users close up shop and
turn off their lights. The Electronic Ballasts we are now using are very
cleverly designed, and give the same amount of light with line voltages from
a low of only 90 volts up to over 140 volts.

Why doesn't everybody use Electronic Ballasts? Probably because Magnetic
Ballasts are cheaper to make and install.

What About High Output And Very High Output Fluorescent Bulbs?

High Output bulbs and Very High Output bulbs are
just bulbs designed for much higher current arcs. A 24 inch long, 40
watt High Output fluorescent bulb needs the same amount of current as
a 48 inch long standard fluorescent bulb. Don't try to use a 40 watt
magnetic ballast on a 24 inch, 40-watt High Output bulb. It probably
will not work. Some newer magnetic ballasts will work, not as well as
a proper ballast, but they will work. Sort of. At least some of our
old ballasts won't work at all with such bulbs. You turn on the light,
and exactly nothing happens. We found both "Hybrid" 40 watt
Rapid Start Ballasts and Electronic 40 watt Rapid Start Ballasts
worked just fine with 24 inch long, 40 watt High Output bulbs. (I
have a friend who is a Licensed Professional Engineer, with a PhD in
Electronic Engineering who told me to try the Electronic Ballasts.) If
you watch Electronic Ballasts as they are starting bulbs, they seem to
work really weird. They "pulse" current through the
filaments to start the bulbs, then turn off the filament current when
the bulbs start. You can see this happen if you only have the pins on
one end of the bulb connected to the ballast. The filaments at the
ends of the bulb glow bright then dim then bright and so on. (This can
happen if you are using those rubber "plug in" special aquarium end
caps. You don't always get the pins lined up just right.)

``Ice Cap Electronic Ballasts are very good ballasts.'' My
friend tells me it is entirely possible to make an Electronic Ballast
that can "sense" what kind of bulb is connected to it, and
automatically regulate the current in the arc to the right level. I
have never tried an Ice Cap, but I would guess they are designed to
operate that way.

Ordinary Electronic Ballasts are a lot cheaper!!!! We are
paying from #39.50 up to about $44.00 each for the Electronic Ballasts
we are using. (That is wholesale from Grainger.) There are
Electronic Ballasts made for all sorts of fluorescent bulbs. You can
get them to light only one bulb. Or, light two bulbs at once. Or,
you can get them to light two or even three bulbs, each bulb lighting
all by itself. The advantage of that is, just because one
bulb "wears out," the others will keep on working all by themselves.
You pretty much get what you want, and are willing to pay for.

Do You Really Get All That Much More Light From High Output Bulbs?

Sort of. There is no such thing as a free lunch!!! The bulbs are
much brighter, but they also draw much more electic current. The
lighting engineers say you want "the most Lumens per Watt," I would
say "Most Bang for the Buck." The bottom line seems to be you get
pretty much the same Lumens per Watt from any Electronic
Ballast with any combination of bulbs. It takes more bulbs
with "standard" 40 watt bulbs, fewer bulbs with High Output and Very
High Output bulbs. The amount of electricity used per actual Lumen of
light output is just about the same, no matter which bulbs you use.
We found here that High Output Bulbs "leak" more Ultraviolet light,
which actually burned some corals before we figured out what was
happening. All Electronic Ballasts are brighter than Magnetic
Ballasts. As far as I know, there are no exceptions to this rule.

Should you buy Ice Caps? Darned if I know! They sure seem
expensive! My Engineer friend thinks they are pretty "pricey." They
work very well indeed, and have some good safety features built
in. They turn off automatically if you have a dangerous current
leakage. So does any properly installed Ground Fault Interrupter.
Tunze makes excellent stuff, so does Dupla. Expensive stuff! Is it
worth the money? Again, I simply do not know.

by "Shimoda, Wade" <WShimoda/hei.com>
Date: Fri, 20 Mar 1998

I recently took a course on efficient lighting taught by someone from
the Lighting Design Lab in Seattle and I thought I'd share some of the
points that might interest you. Although the class covered various
technologies, I'll just cover fluorescent lighting since that appears to
be what most people are interested in.

History:

In the 1970's, the first electronic ballasts appeared.
In the 1980's, compact fluorescents and T8s appeared.

Lamp life and lumen depreciation:

Lamp life is the average or median operational life. e.g., in a sample
of 100 lamps, by the time their total operating hours equals their
operational life, 50 will be burned out.
Lumen depreciation is the fractional loss of lumens at rated operating
conditions that progressively occurs during lamp operation.
At 100% of rated lamp life -
Halogen incandescents have about 95% of their initial lumens
T8 fluorescents (1", or 8/8ths of an inch diameter) - 90% (GEs new
Starcoat lamps (F32 T8) are supposed to maintain 95% of their initial
lumens)
Incandescents - 80%
T12 fluorescents (1 1/2", or 12/8ths of an inch diameter) - 75%

Magnetic ballasts operate with an output (the elec. going to the lamps)
of about 60 Hz.
Electronic ballasts operate at over 25 kHz. People may notice the
flicker of magnetic ballasts, but not of the electronic ballasts.
Electronic ballasts usually run cooler than magnetic ballasts.

Ballast factor - the lumen output of the lamp and ballast combination
compared to the rated output of the lamp on an ANSI reference ballast.
Wattage consumed by the combination is approx. proportional to the
ballast factor.
---Magnetic ballasts - .94 to .95
---Electronic ballast - .65 to 1.28
Note: lamp life may be reduced with ballast factors greater than 1.18.

Rapid start or instant start ballasts.

Instant start ballasts put more stress on the lamp when it's started,
therefore slightly reducing lamp life, but they also use less
electricity. However, at about 12 or more hours of operation per start,
lamps on instant start ballasts have about the same lamp life as those
on rapid start ballasts.